/**
 * 基于下面提供的代码，完成后续的四个练习
 */

const fp = require('lodash/fp')
const {
  MayBe,
  Container
} = require('./support')

// 练习1:使用fp.add(x,y)和fp.map(f,x)创建一个能让functor里的值增加的函数ex1

let maybe = MayBe.of([5, 6, 1])
let ex1 = (num) => {
  let fn = fp.flowRight(fp.map(fp.add(num)))
  return maybe.map(fn)
}
console.log(ex1(1)) // MayBe { _value: [ 6, 7, 2 ] }

// 练习2：实现一个函数ex2，能够使用fp.first获取列表的第一个元素

let xs = Container.of(['do', 'ray', 'me', 'fa', 'so', 'la', 'ti', 'do'])
let ex2 = () => {
  return xs.map(fp.first)._value
}
console.log(ex2()) // do

// 练习3:实现一个函数ex3，使用safeProp和fp.first找到user的名字的首字母

let safeProp = fp.curry(function (x, o) {
  return MayBe.of(o[x])
})
let user = {
  id: 2,
  name: 'Albert'
}
let ex3 = () => {
  return safeProp('name', user).map(fp.first)._value
}
console.log(ex3()) // A

//练习4:使用MayBe重写ex4，不要有if语句

let ex4 = function (n) {
  const m = MayBe.of(n)
  return m.map(parseInt)._value
}
ex4()
console.log(ex4()) //undefined
ex4(1)
console.log(ex4('88')) // 88